[khaos974]

Posted the updated specs from m903_manual_RevA.pdf in the OP.

 

[paulchiu]

just got a call from my dealer
they got the first shipment from grace of the m903
neil at grace design said that they shipped to a number of dealers on feb 9th
i will be getting number 18, well, actually 9300018
i asked for number 1 but grace has the dibs on that one.
 
for the record, i have #...88 of the m902
 
paul

 

[NA Blur]

m903 vs Ultra Desktop Amp / DAC
 
I ran some extensive tests last night using one DAC to feed the other as a headphone amp.  The Grace left a little to be desired for the install as it wanted to install a driver that did not come in the box nor was adequately represented on their site ( as directed to by the manual ).  The Grace runs hot.  I would say a good 15 C above the Ultra Desktop under the same load.
 
The Grace handled most of my phones, but struggled ever so slightly to get the bass impact and extent of my HD-650's.  The clarity, swiftness, and immediacy on the Grace were amazing.  Having an LED display for the volume is hugely useful when doing A / B comparisons.
 
The Desktop did a little better in the soundstaging and had 10% more bass impact with my HD-650's.  With some Grados or ATH-M50's the difference was hardly noticeable.
 
I find the Grace a bit fatiguing compared to the Ultra Desktop.  The Grace does have myriad inputs / outputs which is a huge plus.  Both units fit nicely on top of my PC chassis which is big plus.  I would like to see someone run the Balanced outs ( TRS ) into some HD-800's and see if there is something of interest there.  Anyone?
 
When I am done reviewing both units I will update this post in hopes in shedding some nice white LED light on the questions brought up here.

 

[carrda]

How much break-in time was there on the M903 before your testing?

 

[NA Blur]

I ran it over 30+ hours and I rarely notice major changes in the DAC / Amp stages.  I mainly hear differences when I burn in my headphones.  The m903 seems to heat up nicely in about 10 minutes which I imagine is when it realizes stability.

 

[visualguy]

 
I got my m903 a couple of days ago. I compared the sound quality of both the DAC section and the headphones amp section to those of the Benchmark DAC1 HDR. I used HD800 and HE-6 headphones for the headphones amp comparison. I used an SR-007/KGSS combo and also Focal Twin6 powered studio monitors for the DAC comparison.
 
Bottom line - no significant difference in sound between the DAC1 HDR and the m903. This applies to both the DAC section and the headphones amp section. This is a good thing and what I was hoping for since the DAC1 has excellent sound quality.
 
Since the m903 offers comparable sound quality to the DAC1 at a comparable price, but a better feature set, I would highly recommend it.

 

[NA Blur]

I will soon be answering whether or not one can / should use the balanced outs on the m903 to drive HD-650 headphones.  I tried my stereo plug on one side of the balanced output and hear some extended detail.  The plan is to go from HD-650 to balanced XLR to XLR / TRS adapter.  The headphones will remain balanced all the way to the amp giving the amp yet another option for audiophiles using headphones.

 

[RJ2015]

Did you try the m903 as a pre amp as well?

 

[NA Blur]

I did try the m903 as a pre.  See my review for the m903 for details:
 
http://www.head-fi.org/products/grace-design-m903-reference-headphone-amplifier-dac

 

[NA Blur]

First let me say that the m903 driving a pair of HD-650's does not produce the most pleasant sound. Perhaps this is not the amps fault as much as the general signature of the HD-650, but the very frequency dependant impedance on the lower end of the HD-650 it is not a huge surprise that the m903 leaves ears very bass hungry. One headphone that absolutely sounds amazing from the m903 is the Philips SBC HP910. The bass returns fully extended and impactful. The mids and highs remain even and up-front. With the comfort level of the HP910 surpassing even the Beyerdynamics DT880 velour pads, if you can imagine such madness, is no disadvantage either.
 
One thing I can compare it to is listening to a pair of 500 hour + SR-80's through an Ultra Desktop Amp. It is as if your ears and your amp form a perfect synergy. When you go to work and find yourself thinking "I sure miss my headphones / amp" then you will know what I mean.
 
My next test will be slamming a pair of AH-D2000's into the m903 and doing some more a/b testing.
 
If Grace were to implement a bass boost function into their m903 design the amp would honestly be perfect. This enables the amp, at the press of a button, to enhance the lower end at will.  I do not consider myself a bass head, but having sharp mids and highs without the bass is like fishing in a desert...going to leave your hungry!
 
Seriously, check out the HP910 headphones from your favorite amp.  I still find myself in awe.

 

[khaos974]

Strange, with an output impedance of 1.2 ohm, the  m903 should be absolutely flat as far as frequency response is concerned. What you are hearing is not a frequency balance problem, unless Grace design lied in their specs.

 

[Flea Bag]

Sorry but you must have mistyped below: Was it the Grace you found fatiguing or the Headroom amp?

 
Quote:

I find the grace a bit fatiguing compared to the Grace.  The Grace does have myriad inputs / outputs which is a huge plus.  Both units fit nicely on top of my PC chassis which is big plus.  I would like to see someone run the Balanced outs ( TRS ) into some HD-800's and see if there is something of interest there.  Anyone? 

 

[visualguy]

Quote:

 
I got my m903 a couple of days ago. I compared the sound quality of both the DAC section and the headphones amp section to those of the Benchmark DAC1 HDR. I used HD800 and HE-6 headphones for the headphones amp comparison. I used an SR-007/KGSS combo and also Focal Twin6 powered studio monitors for the DAC comparison.
 
Bottom line - no significant difference in sound between the DAC1 HDR and the m903. This applies to both the DAC section and the headphones amp section. This is a good thing and what I was hoping for since the DAC1 has excellent sound quality.
 
Since the m903 offers comparable sound quality to the DAC1 at a comparable price, but a better feature set, I would highly recommend it.

I've been doing more listening and comparison between the DAC1 and the m903, and I have to amend what I wrote above. I found an area where the m903 has a weakness compared to the DAC1: drums don't sound as good on the m903 as they do on the DAC1. It's very evident when listening to classical orchestral music with drums, such as Beethoven symphonies 5 and 7. This is disappointing... I'm listening to high-end powered studio monitors connected to the balanced outputs (same speakers with both the DAC1 and the m903, of course).
 
I noticed in general that listening to the drum part of the mix is a good way to test equipement. I used to think that it was relevant only to speakers/headphones, but it seems that DACs and pre-amps can also have trouble handling drum sound. Not sure what it is about it that's challenging for the electronics. I can understand why speakers and headphones may have trouble with it, but why DACs and pre-amps?
 
By the way, I also tried the Bel Canto DAC2.5, and it handles the drums better than the m903, but not as well as the DAC1.
 

 

[NA Blur]

 
[size=10pt][size=10pt]Khaos,[/size][/size]
[size=10pt][size=10pt] [/size][/size]
[size=10pt][size=10pt]I believe at this point the lack of bass emphasis with the Grace is a combination of the HD-650 roll off, impedance as a function of frequency on the low end, and the brightness of the amp.  The hardest thing for amps to do, in general, is to produce solid well controlled bass.  Same goes for headphones really.[/size][/size]
[size=10pt][size=10pt] [/size][/size]
[size=10pt][size=10pt]Flea,[/size][/size]
[size=10pt][size=10pt] [/size][/size]
[size=10pt][size=10pt]The Grace is fatiguing compared to the Ultra Desktop.  If you are going for pure sound enjoyment then the Ultra is more pleasant, the Grace is a bit too analytical. [/size][/size]

 

[visualguy]

The m903 is somewhat deficient in bass even through its non-headphones outputs. In other words, at least part of the issue is with the DAC section rather than the headphones amp section.
 
So far all my attempts to find a DAC that matches the sound quality of the Benchmark DAC1 have been in vain... I've been able to match it with high-end Marantz reference players, but not with standalone DACs at a price comparable to the DAC1 (haven't tried DACs over $2K).
 
By the way, what's special about the low frequencies that makes them so hard to be reproduced well by DACs, pre-amps, and amps? I understand why they're problematic for headphones and speakers, but what's the physics or electrical engineering behind the challenge faced by the electronics?
 
Quote:

 
[size=10pt][size=10pt]I believe at this point the lack of bass emphasis with the Grace is a combination of the HD-650 roll off, impedance as a function of frequency on the low end, and the brightness of the amp.  The hardest thing for amps to do, in general, is to produce solid well controlled bass.  Same goes for headphones really.[/size][/size]
[size=10pt][size=10pt] [/size][/size]